Concerns about environments including inhibition of carbon dioxide are socially demanded. As such, there is a growing demand for low fuel consumption of vehicles. Accordingly, there is an increasing demand for materials having superior wet skid resistance, abrasion resistance and breaking strength as materials for vehicle tires, in particular, tire treads contacting the roads.
Meanwhile, carbon black, silica and the like are used as reinforcing fillers for tire treads. When silica is used as a reinforcing filler, advantageously, hysteresis loss is reduced or wet skid resistance is improved. As compared to carbon black having a hydrophobic surface, silica having a hydrophilic surface has a disadvantage of low dispersibility of silica in rubbers due to low affinity to conjugated diene rubbers. Accordingly, use of additional silane coupling agent is required to improve dispersibility of silica in rubbers or form silica-rubber bonds.
In order to solve these problems, functional groups having affinity or reactivity to silica are introduced into an end of rubber molecules to improve dispersibility of silica in conjugated diene rubbers and implement sealing through bonding between the end of rubber molecules and silica particles and thereby reduce hysteresis loss.